About Screenshot Annotator
Drop a screenshot, mark it up, ship it. The Screenshot Annotator gives you arrows, rectangles, circles, highlight blocks, blur regions and text labels — all rendered in real time onto a canvas, all running entirely in your browser. Click-and-drag to draw, click an existing annotation to select it, drag the handles to resize, hit undo if you change your mind. Export as PNG (lossless, with annotations baked in) or JPG (smaller files for chat / email). The annotation engine is shared with the Blur Sensitive Info tool, so the visual quality is identical between the two.
- No uploads
- Browser-only
- Works offline
- 100% free
How it works
- 1
Drop a screenshot
JPG, PNG, or WebP up to 50 MB. The image becomes the base layer; annotations stack on top.
- 2
Pick a tool, click-drag
Toolbar across the top — arrow, rectangle, circle, highlight, blur, text. Click and drag on the canvas to create. Switch to Select mode to move or resize an existing annotation.
- 3
Undo, then export
Cmd/Ctrl-Z undoes the most recent annotation. Cmd/Ctrl-Shift-Z redoes. Export downloads a flattened image — annotations are permanently rendered into the pixel data.
Related tools
Browse allBlur, pixelate or black-bar private regions before sharing screenshots.
Wrap any screenshot in a macOS, Windows or terminal window frame.
Wrap a screenshot in a phone, tablet, laptop or monitor frame.
Crop with aspect-ratio presets — square, 16:9, portrait, freeform.
Frequently asked questions
Are my files uploaded to a server?
No. Every tool on SnapToolz runs entirely inside your browser using JavaScript and WebAssembly. Your file is read locally, processed in memory, and the result is offered as a download. Nothing is sent to a server — there isn't one to send to.
Why does my screenshot look slightly different in the export?
It doesn't — the export uses the canvas dimensions exactly. If you scaled the preview to fit your screen, the export still uses the original pixel dimensions. Compare side-by-side to verify.
Can I edit an annotation after I've drawn it?
Yes. Switch to Select mode (the cursor icon in the toolbar), click the annotation, then drag any of the resize handles or the body itself. The colour and stroke width pickers update the selected annotation in place.
How does the blur tool work?
It captures the underlying screenshot pixels for the region, applies a Gaussian-style blur via canvas filter, and pastes the blurred patch back into the export. The blur is rendered fresh on every export so it stays sharp at the canvas's native resolution.
Does it work offline?
Yes. SnapToolz is a Progressive Web App. After your first visit, the app is cached on your device and every tool keeps working without an internet connection.
Is SnapToolz free?
Yes — every tool is 100% free with no sign-up, no watermark, no hidden tier. The whole platform is open source and we have no plan to gate features.